1. Field of the Invention
The present invention relates to an actuator, and in particular to a gear motor having a safety mechanism.
2. Description of Prior Art
A transmission mechanism is widely used in various apparatuses such as electric sickbeds, treadmills, electric tables or the like for adjusting their height or inclination angle. The starting point and the terminal point of the stroke of the transmission mechanism are often provided with a touch switch respectively. When the transmission mechanism moves along its stroke and contacts the touch switch provided at the starting point or the terminal point, the touch switch will shut off the electricity supplied to the transmission mechanism, so that the transmission mechanism can stop operating at the terminal point or the starting point. In this way, the transmission mechanism can be prevented from idling or wearing at the starting point or the terminal point, thereby increasing the safety in use of such an apparatus having the transmission mechanism.
As shown in FIG. 1, the conventional linear actuator includes a gear motor 10 and a driven mechanism 20 connected to the gear motor 10. The driven mechanism 20 comprises a coupling rod 201, an output rod 202, and an annular block 203. The coupling rod 201 is threadedly connected to the output rod 202. The annular block 203 is fixed to the output rod 202. The gear motor 10 drives the coupling lever 201 to rotate, thereby driving the output rod 202 and the annular block 203 to move accordingly. Further, a first touch switch 30 and a second touch switch 40 are arranged to correspond to the output rod 202, so that the linear actuator 10 can be stopped operating when the annular block 203 contacts the first touch switch 30 or the second touch switch 40.
However, in practice, the above linear actuator still has following problems. The standard of the driving mechanism 20 of the linear actuator is different, so that the final position of the first touch switch 30 or the second touch switch 40 has to be varied. Thus, the manufacturers in this field have to prepare various combinations of the driven mechanisms 30 and touch switches, which increases the stocks and the difficulty in managing inventory. When the travelling distance of the output rod 202 is larger, the volume of the driven mechanism 20 will be increased because the first touch switch 30 and the second touch switch 40 have to be positioned to correspond to the output rod 202, and thus the whole linear actuator becomes bulky.
In order to solve the above problems of prior art, the present Inventor proposes a novel and reasonable structure based on his expert knowledge and deliberate researches.